In the prior art, bulk dry material was typically shipped in many different kinds of containers and then those containers were discarded after the bulk material was received by the end user and loaded into other bulk storage facilities including bins or the like. For many reasons including cost, soft-sided, high strength, multiple layer bags utilizing liners have been recently developed and are gaining in popularity for the shipment and handling of significant quantities of bulk dry material. The inventors herein are aware of uses in the food industry where the dry material contained in the bag typically approaches 3,000 lbs., with a bag standing 3-4 feet in height with a square base between 2-3 feet on a side. For shipment, these bulk bags are typically skid mounted so that a forklift may conveniently be used to handle the bag by lifting the skid and moving the bag as desired. Strap-like lifting handles are typically provided at the four corners at the top of the bag, but the inventors are unaware of any prior art use for these handles other than to facilitate grasping of the bag by several men for manually adjusting the position of the bag on the skid or the floor. These lifting straps are sufficiently sturdy to permit lifting of the bag and its contents thereby, and it is presumed by the inventors that overhead cranes or fork lifts or the like may be used in some installations for transporting the bags and/or contents within a plant or other facility.
Typically, at least in one application, these bulk bags have a pour spout integrally formed therein and located near the center bottom of the bag such that the bag may be positioned off the floor and on some type of weighing, batching, or mixing apparatus for dispensing of the dry material directly from the bulk bag. For these applications, it is typically required to lift the bulk bag and its contents from the floor or other storage facility, up and onto the particular piece of equipment being utilized to dispense the dry material. For these applications, it is particularly difficult for a forklift truck to lift the bulk bag and put it in place on the machine. Typically, as might be expected, the underlying skid cannot be used as it would block the bottom pour spout of the bag. Therefore, as best known to the inventors, the forklift operator typically scoops the bulk bag off the skid by placing the forklift blade beneath the bulk bag and the skid. This involves considerable risk of tearing of the bag or otherwise damaging the bag and thereby ruining it for its intended purpose. Additionally, these bulk bags can be quite unsafe when lifted to any appreciable height as the bag typically leans to one side and is unsteady, and the contents thereof may readily shift as the bag is lifted. Furthermore, movement of the bag tends to cause the contents to shift in an unpredictable manner such that the bag is not strictly aligned. For some equipment, this makes it difficult for a forklift truck operator to place the bag properly as limited space may be provided therefore in the equipment.
In order to facilitate the support and lifting of the soft-sided bulk bags by forklift trucks, one of the inventors herein has previously succeeded in designing and developing a bird cage-like framework which may be set over the top of a bulk bag to surround it, with the framework having four hook-like strap supports located at its corners to which the bulk bag's straps may be affixed. Additionally, a pair of rails comprised of inverted U-brackets extend along the top of the framework from the front to back thereof to provide a convenient structure to receive the blades of a forklift truck so that the framework may be conveniently handled thereby. Additionally, a bracket lip may be formed by a set of horizontally extending brackets surrounding the outside of the framework and immediately above the ground such that the framework may be lifted and placed onto a receiving bracket lip mounted to the user's equipment so that the framework may be used not only to support and lift the bulk bag and its contents, but also to mount it to a bulk storage and dispensing machine such as a batch weighing apparatus or the like.
As can be appreciated, many of the problems in the prior art have been solved by the framework invention. For example, the forklift blades need not be shoved between the bottom of the bag and the skid which thereby eliminates risk of damage to the bottom of the bag and pour spout. As the bag is lifted by handling the framework, minimal physical contact is made with the bag which further reduces accidental tearing, or other damage to the bag caused by shifting of the contents thereof. Lifting the framework from the top causes the bag to "sag" to the center of the framework and forces the straps to support the bag relatively evenly to thereby facilitate placement of the bag and framework on a user's piece of equipment. By placing the bag on a skid whose dimensions are smaller than the framework, the bag may be easily secured to the framework, lifted off the skid, and thus be suspended off the ground by the framework for easy placement on other equipment. Furthermore, the outer dimensions of the framework define an envelope required on the equipment for placement of the bag and which the user may rely on from bag to bag regardless of the shifting contents thereof or tilting of the bag on the forklift as is experienced in the prior art.
In using the framework invention for suspending bulk bags and rack mounting them on a batch weighing device for direct dispensing of material from within the bulk bag, the inventors have found that the interior liner of the bag has a tendency to interfere with flow of the material. As the material is dispensed from the bag, the interior liner has a tendency to elongate and collect at the bottom thereof at which point it clogs the pour spout or bulk bag discharge opening at the bottom thereof. Elongation of the bag is essentially caused by three things. First, the diameter of the liner decreases as material is dispensed from within the liner, thereby causing the liner to elongate. Secondly, the liner is generally made from flexible materials which have a tendency to stretch, especially when loaded with a bulk of dry material. Thirdly, there is a natural tendency for the liner to drop down into the pour spout or bulk bag discharge opening because of gravity and the movement of material which creates frictional forces having a tendency to pull the liner towards the bottom of the bag. For these reasons, additional attention by an operator has to be given to the bulk bags after they have been rack mounted in order to ensure that the discharge openings are clear and free flowing. Thus, while the bulk bag support framework previously developed has provided a marked improvement over the prior art, the inventors have worked towards eliminating this last bit of operator involvement so that the bulk bags might conveniently be used in place of rigid walled storage bins.
In actual usage, if a liner would hinder or block a discharge opening, an operator would typically be forced to cut through the sidewall of the bulk bag in order to free the liner and clear the discharge opening for continued free flow of material. However, cutting the bulk bag eliminates its potential reuse through reinserting a new liner in the bulk bag and refilling it as is customarily done in the prior art. Thus, there is a cost savings which can be achieved if the liners can be prevented from migrating into the discharge opening, thereby eliminating the need to cut open the sidewall of the bulk bag and thereby eliminate its reuse.
In order to further enhance the prior invention of the bulk bag support framework, and to solve the additional problems noted herein, the inventors herein have succeeded in designing and developing a liner hoist which is elegantly simple and which serves to either secure the liner in place or automatically retract the liner upwardly out of the bulk bag and away from the discharge opening and pour spout at the bottom thereof as material is emptied from within the liner. The liner hoist of the present invention includes in a first embodiment a rope with a hook attached at an end for insertion through an eyelet formed from the upper end of the liner. In a second embodiment, the invention further includes a plurality of pulleys for supporting the rope from the bulk bag support framework, a cleat for releasably securing the rope at a fixed length, and a spring extending between the rope and the framework.
In operation, the upper end of the bulk bag liner is twisted into a rope-like length, doubled over to form a loop, and then secured by a plastic tie wrap or the like to form an eyelet. The hook of the liner hoist is hooked into the eyelet and the rope is then tied off directly above the bag and to the framework. As the rope is tied off, it is pulled tight and has been found to adequately retain the liner in place as material is dispensed. With the second embodiment, instead of tying, the rope is pulled tight around the pulleys to tension the spring, the rope sliding through the cleat so that upon reaching spring tension, the rope may merely be released and then be held in place by the cleat. Then, as material is discharged from the bulk bag and the liner elongates, the mechanical force of the spring in combination with a pulley, which provides a two to one mechanical advantage, pulls the rope to lift the hook and eyelet and withdraw the liner from within the bulk bag. With the liner hoist of the second embodiment, the liner is withdrawn from the bulk bag as it elongates to thereby prevent its interference at the bottom of the bag with the discharge opening and pour spout. The second embodiment thus actively withdraws the liner from within the bag and is preferred over the first embodiment.
While the principal advantages and features of the present invention have been described above, a more complete understanding thereof may be attained by referring to the drawings and description of the preferred embodiment which follow.